Disclaimer: All data summaries and exploration presented here are preliminary and may not be indicative of the final data that will be incorporated in the 2023 assessment models
Description of data and model specification being considered for use in the 2023 assessments for black rockfish off Oregon.
The last assessment of black rockfish rockfish in waters off of Oregon was conducted in 2015 and estimated stock status for that year at 60.4% (Figure \(\ref{fig:dep2015}\)), and never showed a decline below the target biomass (Figure \(\ref{fig:ssb2015}\)). This assessment was highly constrained by the choice to treat the catchability of the tagging index as known, thus the uncertainty in the assessment is very low. The complete assessment document can be found here.
Since several years have passed from the last assessment model, the Stock Synthesis (SS) modelling framework has undergone many changes. While the specific changes in the model can be found in the model change log, here we simply update the model from the older 3.24V version to the newer 3.30.20 version. The point here is to present any differences in the model outputs when using the same information. This was first done by migrating the data and parameter specifications from the former files to the newer files. This migration was assisted using the SS-DL tool. Once the old data was transferred to the SS 3.30.20 file, two versions of the model were run.
Results are similar between models when all parameters are fixed from the 2015 model in the updated SS files, while there are slight scale differences (Figure \(\ref{fig:ssb_comps}\)), but little relative stock status differences (Figure \(\ref{fig:ssb_deps}\)), when the new SS version is allowed to estimate the same parameters as estimated in the 2015 version. Theses model comparisons are adequate to move ahead using the newest version of SS 3.30.20 without expecting large differences in reference models being due to versions of SS.
The stock structure of black rockfish continues to be based on state-specific boundaries. Stocks definitions are based on a variety of factors that include genetics, biology, ecology, habitat availability and fishing mortality history. Black rockfish range from southern California up to Alaska. There ecology as a nearshore (i.e., commonly an area of restricted gene flow) rockfish with semi-pelagic behavior (e.g., can demonstrate rare, but substantial adult movements) under strong and differential fishing pressure by state provides an interesting assortment of considerations. A recent genetics study done by Hess et al. (in review) found that Alaskan and west coast populations showed significant genetic difference. The population from Washington to California showed a variety of interesting genetic signatures, with decreased genetic diversity north of Cape Mendocino and North of the Columbia River, but increasing in waters off of Oregon. There were also pockets of isolation by distance and odd signatures off Brookings, Oregon. These variable genetic signatures combined with the lack of consistent black rockfish habitat in southern Washington, and the different exploitation histories in each of the states made state-level designations to support management decisions the most logical. This does not suggest there is no exchange of individuals among California, Oregon and Washington, but instead acknowledges that the exchange is likely low enough not to homogenize the populations, and that different population trends can be expected in each state. This was supported in the results of the last assessment, where important differences in stock status were observed.
Currently, the following fleet structure is being considered for modeling commercial and recreational fisheries in both area models:
Defining fleets is largely based on whether a fishing approach differs in the selectivity (i.e., the capture of fish by length and/or age). Selectivity translates how the removals are taken via length and/or age out of the population. The above four fishery types are distinguished by different fishing activities that result in different selectivities. While in the past the commercial fixed-gear fisheries had been separated by the condition of the landed fish (dead and live), it has been determined that the designation of how the fish will be delivered is a processing issue, not a capture/selectivity issue. Thus the gear selectivity is considered the same in this fleet. This similarity in selectivity is apparent when looking at the 2015 assessment selectivity estimates. For the recreational fishery, the private and charter boat-based fisheries show similar aggregate length compositions and are treated as one fleet (Figure \(\ref{fig:private_charter_lts}\)). The boat- and shore-based fleets show distinct aggregate compositions that demonstrate the well known characteristic of shore-based landings catching smaller fish (Figure \(\ref{fig:boat_shore_lts}\)). These recreational fleets are the same treatments as in the 2015 assessment.
Black rockfish are not considered a major commercial species, but historical reconstructions have shown prominent trawl catches in the past that have subsequently waned over the last 40 years. Historical catch reconstruction were done for the 2015 assessment, and are heavily based on applying highly variable catch compositions to years that do not have those composition, but rather just report total or “unknown” rockfish catches.
When providing data to the 2015 Black rockfish assessment, ODFW staff noted that trawl landings from the 1940s to the 1980s had high year to year variability and an unreasonable magnitude of landings in some years. These data were from the then newly completed Karnowski et al (2014) catch reconstruction. ODFW provided an alternative time series that was eventually used in the 2015 assessment (P. Mirick (ODFW) was the main source of this reconstruction). Additionally, the Karnowski et al. (2014) reconstruction did not account for fish taken off of Washington but landed into Oregon, specifically Astoria port landings. The Mirick reconstruction substantially reduced the magnitude of historic trawl catches and stabilized interannual variation in landings compared to the Karnowski et al. (2014) reconstruction. Total rockfish 3A landings were of similar magnitude between the two reconstructions, though different data sources were used in each approach. Species compositions, though, were from the same dataset (Douglas report), but differentially applied. The annual Douglas compositions were used for the Karnowski reconstruction, but these annual compositions were pooled for the Mirick reconstruction. Comparisons of 3A black rockfish from the Douglas report are different than in the Mirick reconstruction but of similar magnitude.
As a part of the 2015 assessment, trawl landings from 3A were also split between OR and WA by using the pooled Douglas compositions and other ODFW sources of information. Static average percentages of black rockfish were applied over multiple decades to allocate fish to WA. The STAT team is still considering the best magnitude of black rockfish in area 3A (dependent on the assumption of black rockfish composition within the to unknown rockfish category) to apply to this OR-WA split. The STAT is also considering further information that may confirm the level of black rockfish in 3A that are landed in Astoria but should be assigned to the Washington state history.
Only the commercial landings are shown for each area. Discard mortality across time will need to considered to determine catches.
The recreational landings
T ### NWFSC West Coast Groundfish Bottom Trawl Survey
The majority of lengths are from hook and line gear for each area:
The recreational length composition data summarized below represen data pulled from RecFIN collected by either the MRFSS (1980 - 2003) or CRFS (2004 - 2022) sampling programs. There are additional data sources that contain historical length samples from the CPFV fleets (1975-1979 from Collins and Crooke, 1987-1998 from Deb Wilson-Vandenberg, and 1986-1989 from Alley and Ono) that will be evaluated and used within each assessment model as appropriate but are not included here.
The total number of length samples within RecFIN across MRFSS and CRFS are:
In RecFIN there are lengths from shoreside modes that were not included in the analysis presented below (north of Point Conception = 148 and south = 20). All lengths below represent released fish. There were limited length observations of released fish (north = 52 and south = 187).
TODO: Add table and figures showing the around the number of single day and multi-day trips
TODO: Add figure showing the two maturity curves from last assessment.
TODO: Add fecundity-at-length figure based on Dick et al. that was assumed in the last assessment
TODO: Add information on additional maturity and fecundity samples being collected that will be used to update both maturity and fecundity if information is available in time.
The length-weight relationship was estimated using all biological data available from the NWFSC West Coast Groundfish Bottom Trawl (WCGBT) and the NWFSC Hook and Line surveys.
TODO: Add plot showing the length-at-age of available data by area
TODO: Add table of the number of additional age reads by sources that the CAP lab is working on
Natural mortality was fixed in the 2021 assessments at a value of 0.108 yr-1 based on an assumed maximum age of 50 years. The maximum age was selected based on available age data collected within Oregon and Washington and literature values. The oldest aged observed was 51 years with two observations off of the coast of Washington and Oregon in 2019. This selection was consistent with the literature examining the longevity of copper rockfish and was supported by the observed ages that had multiple observations of fish between 44 and 51 years of age.
The input parameter value for natural mortality will be reconsidered within the 2023 assessments based on any new available age data. Additionally, the 2023 assessments will explore the ability to estimate natural mortality within the model and will conduct sensitivities and profiles to understand the information in the data on natural mortality and the impact of select values on the model estimates.